Hemoglobinopathies are among the most common genetic disorders. In utero hematopoietic transplantation (IUHCT) is a promising strategy that offers the benefit of treating congenital diseases prior to birth. IUHCT takes advantage of a naive host prior to immune maturation to introduce donor cells. The success of IUHCT has been limited to recipients with severe combined immunodeficiency disorders in which there is a selective advantage of donor cell engraftment over host cells; however, levels of engraftment of donor cells have not been therapeutic for diseases in which the donor cells have no survival advantage. Thus, there is a critical need to increase donor cell engraftment after IUHCT in diseases where there is little or no competitive advantage for the donor cells. We propose to develop novel engineered exosomes to deliver sustained-release drugs to the hematopoietic stem cells, and increase engraftment of donor cells in IUHCT. We hypothesize that thiol modified exosomes loaded with adjuvant drugs will enhance the therapeutic potential of HSCs in IUHCT. Our hypothesis is based on scientific premise that synthetic nanoparticles containing GSK3b inhibitor and drug-carrying multilamellar vesicles facilitate increased engraftment of HSCs in experimental models. The engineered exosomes will be loaded with GSK3b inhibitor and decorated with maleimide to enhance binding of the exosomes to HSCs that are enriched with thiols on their cell surface. We propose the following specific aims: Specific Aim 1: To engineer exosomes from peripheral blood and bone marrow and characterize the engineered exosomes. Exosomes from maternal peripheral blood and bone marrow will be loaded with GSK 3b inhibitor and decorated with maleimide. We will characterize the engineered exosomes for their size, drug loading, surface modification, zeta potential and drug release kinetics. Specific Aim 2: To determine the binding of engineered exosomes to HSCs, assess toxicity and function of the exosome conjugated HSCs and effect of exosome delivered GSK3b inhibitor on engraftment of HSCs in mice. We will determine the hematopoietic engraftment of donor cells in mice, and the ability of GSK3b inhibitor, delivered through the exosomes, on engraftment of donor cells and repopulation capacity. Specific Aim 3: To validate engineered exosomes as an efficient therapy in comparison to the multilamellar nanoparticles. We will perform IUHCT with engineered exosomes and the established lab model of multilamellar nanoparticles to determine the therapeutic potential of the two modes on increasing engraftment of HSCs. The outcome of these studies will be the development of a novel strategy that will utilize a native nanocarrier to deliver therapeutic agents to HSCs, to increase engraftment in congenital diseases where donor cells do not have a selective advantage. The proposed studies are innovative in that utilizing exosomes as delivery vehicles for adjuvants in cell based therapies has not been attempted previously. The positive impact of our studies will be improved therapeutic interventions for congenital diseases.